This invention relates, in general, to steam turbinegenerator power plants; and, in particular this invention relates to feedwater preheating by means of solar energy.
In a steam turbine-generator power plant, a steam generator, or boiler, is used to provide steam for driving the steam turbine which in turn, drives the rotor of an electrical generator to produce electricity. Steam which is exhausted from the turbine is thereafter condensed and returned to feedwater. The feedwater is then recirculated to the steam generator where it is reheated to provide more steam. It has been found economical to preheat the feedwater prior to its return to the steam generator using extraction steam from various points on the steam turbine as a heat exchange fluid. Preheating feedwater raises the temperature of the feedwater and thereby decreases the heating requirements in the steam generator resulting in a decrease in fuel requirements in the steam generator. Of course, extraction of steam from the steam turbine decreases the power output of the turbine, but such a power loss is acceptable in terms of satisfying the load demand and preferable in terms of overall plant efficiency.
According to one aspect of the present invention, it has been found that feedwater may be preheated by applying solar heat to the feedwater. Dependent upon ambient conditions, solar energy may be used to preheat feedwater and thereby decrease the extraction steam requirements in a manner to be disclosed as part of the present invention. Since solar energy is available only on an intermittent basis, it is required that a system be devised which will take advantage of available solar energy while maintaining a capability to meet load demand requirements when solar energy is not available.
Hence, it is one object of the present invention to provide a power plant wherein feedwater preheating is augmented or replaced by solar energy.
It is another object of the present invention to provide a power plant wherein solar energy is delivered into the power plant as it becomes available.
It is another object of the present invention to provide a power plant wherein the turbine power output may be increased without an increase in boiler fuel requirements.
It is still another object of the present invention to provide a power plant wherein the turbine power output may remain constant and the boiler fuel requirements decreased.